Micro Electromechanical System (MEMS) switches are widely used in RF communication systems such as, for example, phased array antennas, phase shifters, switchable tuning elements, and radar sensors. Generally, MEMS switches have features such as low insertion loss, low power consumption, low cost, small size, wide bandwidth operation, long lifetimes and fast switching speeds not found in conventional solid state switches (e.g., FETs or PIN diodes). Specifically, a high quality MEMS switch should ideally have as many of the following features as possible: low activation voltage, high switching speed, long operation lifetime, good isolation from the output signal during an OFF state, low contact resistance and high contact force between the contact electrodes during an ON state, little or no stiction problems at the contact area for easy separation, low power consumption during the switching between different states, little or no power consumption to maintain the switch at a certain state, low cost, ease of fabrication, and ease of switch integration with other coplanar circuitry components.
MEMS switches can be classified into several major categories based on actuation methods including electrostatic, electromagnetic, or electrothermal switches. Conventional MEMS switches that fall into one of these categories exhibit some of the above mentioned high quality MEMS switch features. However, none of the conventional switches exhibit all of the above features.
Further, with respect to electrostatic switches, these switches have the distinct advantage of zero power consumption when toggled or maintained at a given state. However, electrostatic switches also have several disadvantages such as slow switching speed (on the order of psec to msec), relatively high actuation voltage (10-80 V), stiction problems when the contact electrodes are welded together upon physical contact, relatively short lifetimes (100 million cycles for cold switching), and instability problems due to thermal and fabrication related stresses.
Accordingly, an object of the present invention is to provide an electrostatic MEMS switch that exhibits all of the above mentioned ideal switch features and that is free of the above mentioned disadvantages.
It is also an object of the present invention to fabricate such a MEMS switch by a simple process.
It is a further object of the present invention is to provide an electrostatic MEMS switch with a configuration that permits multiple throws and multiple poles.